The invention relates to a swivel apparatus for the transfer of at least one pressurized process fluid, comprising a central stem on which there are placed a number of ring elements comprising at least one outlet ring having a number of outlets communicating through an annulus with an associated course in the stem, and a number of supporting rings of which at least one is stationarily arranged on the stem, dynamic sealing means for sealing against the annulus being arranged between mutually movable ring elements, and bearing means for mutual support for the ring elements.
A swivel apparatus of the above mentioned type is shown and described in the non-prepublished Norwegian patent application No. 981379. This swivel apparatus comprises a number of annulus elements of which each consists of a so-called intermediate ring and an outer outlet ring defining between them an annulus for fluid transfer. The intermediate ring is stationarily arranged on the stem, and on each side thereof there is arranged a bearing ring which is provided with a bearing for support in relation to the intermediate ring. Further, between the intermediate ring and each bearing ring there are arranged axial, dynamic seals which are integrated in the bearing rings. Between the stem and the intermediate ring there are arranged radial static seals, and radial static seals are also arranged between each of the bearing rings and the outlet ring, for sealing against fluid from the annulus. The latter static seals are located at a relatively large distance from the stem, because of the fact that the intermediate ring must have a radial extension which is sufficient for accommodating both the bearing means and said dynamic seals. The bearing rings in which the dynamic seals are integrated, here are fixed or supported at only one place, and deformations in the sealing zones in some fault situations will be a limiting factor.
As regards the radial static seals, it has turned out that deformations and expansions, because of temperature gradients and because of internal pressures in the area around the seals, is a substantial factor putting operational limitations on the swivel.
It is a general object of the invention to provide a swivel structure making it possible to extend the operational limits for the swivel with respect to rate of flow, pressure and temperature, and which also implies a simpler construction and assembling, and therewith reduced manufacturing costs.
Another object of the invention is to provide a swivel structure wherein some of the previously used, critical seals are removed, and wherein the ring elements in the region in which the dynamic seals operate, are better fixed or supported, something which implies that the seals operate under more optimal conditions.
A further object is to provide a swivel structure which is suitable for building of multi-course swivels having quite independent courses, and which also enables that the production through some courses in such a swivel can be maintained during replacement or service of the other swivel courses.
For achieving the above-mentioned objects there is provided a swivel apparatus of the introductorily stated type which, according to the invention, is characterized in that, between the stem and the outlet ring, there is arranged a distance ring which is stationary relative to the stem, and that, on each side of the outlet ring, there is arranged a supporting ring which is stationary relative to the stem and which is axially supported both by the distance ring and an axial bearing arranged at a radial distance therefrom between the supporting ring and the outlet ring, a dynamic sealing means between the outlet ring and each adjacent supporting ring being arranged in the region between the distance ring and the axial bearing in question.
In an advantageous embodiment of the swivel apparatus, the distance ring comprises a plurality of radial holes communicating with an annulus-forming peripheral groove in the stem, and with a ring groove in the adjacent end surface of the outlet ring. Further, the outlet ring at its outer end preferably is provided with a pair of axially oppositely directed ring flanges bordering respective ones of the supporting rings, a radial bearing being arranged between an inner surface of each ring flange and an adjacent surface portion of the supporting ring in question.
As will be seen, the ring elements around the dynamic seals in the present structure are supported at two places, viz. both in the distance rings and the axial bearings, and this will imply substantially smaller deformations, something which is one of the most important presuppositions for securing an operationally safe sealing and swivel system.
In the swivel apparatus according to the invention, the individual ring elements have been changed with respect to design and function, as compared to the known swivel structure described above. The stated sealing arrangement with axial and radial bearings sees to it that the relative movements and frictional conditions are controlled. Because of the configuration of the outlet rings, in addition to the fact that there are no statical radial seals in connection therewith, the outlet rings can be dimensioned for large rates of flow in combination with high pressures and a high temperature gradient.
As a result of the fact that only the outlet rings are rotatable in relation to the centre stem, whereas the remaining ring elements are stationarily arranged on the stem, the fluid courses in the present swivel structure will be independent of each other. Thus, one may operate with independent courses in the swivel, something which implies that one can make use of only the number of courses for which there is a need at any time. The unused courses or spare courses may be pressure relieved and without rotation during operation of the remaining courses, so that one avoids unnecessary wear of parts having a limited working life. This is a substantial advantage in relation to the prior art.